This invention relates to elevated liquid storage tanks and methods of constructing same.
In the past, it has been common practice to construct elevated liquid storage tanks, which are sometimes referred to as water towers, either out of concrete or structural steel. An economical form of concrete storage tank is a simple concrete cylinder which may be completely hollow, or it may be formed with an elevated concrete, floor, the tank of course being that part of the cylinder above the floor. A difficulty with this type of storage tank is that it lacks aesthetic appeal. Also, in cold climates it is usually not desirable to have the concrete in contact with the liquid being stored, because freezing and thawing can have a deleterious effect on the concrete. Of course, a liner or some form of coating could be used to protect the conrete, but this increases the cost of the storage tank considerably and can cause maintenance problems, especially if leaks appear in the liner or coating.
An all steel elevated storage tank is sometimes better than a concrete storage tank from the point of view of water tightness and associated maintenance problems. Most elevated steel storage tanks, however, are supported on structural steel tower structures which are themselves aesthetically unappealing, not to mention the maintenance problem of having to periodically paint the structural steel tower.
As an improvement over the all steel or all concrete constructions elevated storage tanks have been made where the tower or column part is formed of concrete and the tank itself is formed of steel. Ordinarly, it would be very costly to fabricate a steel tank on the top of a concrete tower, but a method has been used in the past to construct a major portion of the steel tank at ground level and hoist same into position at the top of the concrete tower, where a concrete tank floor is poured to interlock the steel tank and the concrete tower. This prior art method of construction is described in the applicants' previous Canadian Patent No. 1,091,883 and U.S. Pat. No. 4,312,167. The construction of the storage tank itself is described in applicants' previous Canadian Patent No. 1,091,884 and U.S. Pat. No. 4,327,531. While the liquid storage tanks described in these patents are aesthetically appealing, economical to produce and relatively maintenance free, the elevated storage tank and method of construction of the present invention is an improvement thereover, in that the storage tanks of the present invention are even more economical to produce, and if desired, the tank portion can be made into a continous steel water containment chamber, so that none of the structural concrete comes into contact with the liquid in the tank.